Thailand's latest spectrum auction raised THB41.3 billion ($1.3bn) this week.

Spectrum in the 1,500 MHz, 2,100 MHz, and 2,300 MHz bands was purchase by True Corp and AIS.

Indeed, the two telcos were the only companies that took part in the auction.

During the auction, held by the National Broadcasting and Telecommunications Commission (NBTC) on Sunday, AIS's subsidiary Advanced Wireless Network (AWN) acquired two blocks of 15 MHz in the 2,100 MHz band for THB14.9 billion ($460m).

True Corp invested even more, spending THB21.8 billion ($672m) on 70 MHz of 2,300 MHz spectrum, plus an additional THB4.7 billion ($144m) on four blocks of the 5 MHz in the 1,500 MHz band.

However, not all the spectrum up for offer was sold. There were no bids submitted for the 850 MHz band, while two blocks of 5 MHz spectrum and seven 5 MHz blocks of 1,500 MHz spectrum also went unsold.

True Corp and AIS hold a duopoly over the Thai mobile market. True currently serves 48.5 million customers, while AIS has close to 46 million subscribers.

There were three established carriers in the country until two years ago, when True Corporation and Total Access Communication (DTAC) completed a long-awaited merger.

The NBTC approved the merger, voting in favor of the deal by 3 to 2, with QCOnline reporting at the time that the casting vote came after 10 hours of deliberation.

A third carrier, National Telecom, was created in 2021 following the CAT Telecom and TOT Public Company Limited merger. State-owned National Telecom has significantly less market share, with around 3 million customers.